JPS6046794B2 - heating device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a heating device suitable for use in, for example, a high frequency heating device.

Hereinafter, an embodiment in which the present invention is applied to a high-frequency heating device will be described. As shown in FIG. A high frequency signal of, for example, 20 to 30 [KH2] is supplied via the drive circuit 3, and a high frequency current is passed through the heating coil 4 connected to the anode of this GCSI, and as shown in FIG. A cooking pot 5 as a heated object
When the pot is placed in it, an eddy current is generated in the pot to heat it up.

The cooking pot 5 is placed on a ceramic plate 6 placed on the top surface of the spiral heating coil 4. Further, 7 is a damper diode for forming a current path when the GCSI is off, and 8 is a capacitor for resonance. A power supply voltage obtained by rectifying a commercial power supply by a rectifier circuit 9 is supplied to the output circuit including the GCSI, heating coil 4, etc. via a filter circuit 10. The rectifier circuit 9 has a bridge configuration in which a current path during the positive period of the commercial power supply is formed by an SCR 11a and a diode 12a, and a current path during the negative period is formed by an SCR 11b and a diode 12b.

The gates of these SCRs 11a and 11b are connected to the trigger circuit 1.
It is connected to the output terminal of 3. The trigger circuit 13 generates trigger pulses for the SCRIla and llb in synchronization with the commercial power supply, and controls the SCR1 by a control voltage from the output control circuit 14 or the heat retention control circuit 15.
A trigger pulse is generated that places 1a and 11b into three operating states. That is, one of them is SCRlla and 1
1b is in an output-off state in which no trigger pulse is supplied to it, and therefore no power is supplied to the output circuit.
The second operating state is SCRlla or 1 when the output is on.
Only one of the SCRs 1b is turned on and the rectifier circuit 9 performs a half-wave rectification operation, and the third operating state is a state in which the output is on and all SCRs 1b and 11b are turned on during the positive and negative periods of the commercial power supply, respectively. It performs wave rectification operation. The output control circuit 14 includes a variable resistor 1 for output adjustment.
6 is provided.

In addition, the heat retention control circuit 15, which will be explained in detail later, is provided with a variable resistor 17 for adjusting the heat retention temperature, and a cooking and heat retention mode switching switch S1 that is linked with the variable resistor 16, and a tempura mode switch in the heat retention mode. S2 is provided. Furthermore, the control voltage of the output control circuit 14 in the heat preservation mode is obtained from the control voltage output terminal 37 provided in the heat preservation control circuit 15, and the control voltage of the trigger circuit 13 is obtained from the on/off control voltage output terminal 44. . The heat retention control circuit 15 is also provided with a temperature adjustment variable resistor 17 and a tempura mode switch S2. As shown in FIG. 2, a thermistor 18 for detecting the temperature of the pan 5 is attached to the plate 6, and a thermistor 19 for detecting the temperature of the heating coil 4 is attached to the lower surface of the heating coil 4. These thermistors 18 and 19 are connected to terminals 18a and 19a of the heat retention control circuit 15. These terminals 18a and 19a are respectively provided in the heat retention control circuit 14. The temperature control variable resistor 17 is connected to the Schmitt circuit 39, which will be described later. In FIG. 1, variable resistor 16 and switch S1 are interlocked.

In the cooking mode in which the slider of the variable resistor 16 is at a position other than the end, the sweets. A movable contact a of the switch S1 is connected to a fixed contact c. At this time, a control voltage is supplied to the output control circuit 14 from the variable resistor 16. Next, when the slider of the variable resistor 16 reaches the end, the heat retention mode is entered and the movable contact a of the switch S1 is connected to the fixed setting b. child·
At this time, the control voltage cannot be obtained from the variable resistor 16, and the terminal 3
A control voltage set by the variable resistor 17 at the output terminal 7 is obtained, and this is supplied to the output control circuit 14. The detailed structure and operation of this heat retention control circuit 15 will be explained later. FIG. 3 shows the main parts of the operation surface of the high-frequency heating apparatus of this example, in which 26 shows an output adjustment knob, 27 shows a temperature adjustment knob, and 28 shows a tempura button. By turning the output adjustment knob 26 clockwise, the position of the slider of the variable resistor 16 is changed, for example, when the output power is 30
It is made to be continuously variable in the range of 0W to 1200W. When this output adjustment knob 26 is turned one full turn to the left (FIG. 3 shows this state), the slider of the variable resistor 16 is located at the end, and the switch S1 for switching the cooking and warming modes is turned to the The mode is switched from the cooking mode shown in FIG. 1 to the warming mode. A temperature adjustment knob 27 is provided on the left side of the output adjustment knob 26, and by turning the temperature adjustment knob 27, the position of the slider of the variable resistor 17 is varied, and the temperature for keeping warm can be adjusted, for example. The temperature can be varied within the range of 60'C to 100°C. When the tempura button 28 is further pressed, the tempura mode switch S2 is switched, and at this time, the temperature for keeping warm is changed to 100°C higher than the normal temperature, and the temperature is 160°C to 200°C. This temperature is in the range that is often used for general cooking or tempura.In addition, there is a display lamp group 29 for output display, a display lamp 30 for displaying warm mode, and tempura mode. An indicator lamp 31 is provided for display.In such a high-frequency heating device, the output power can be controlled by turning the output adjustment knob 26 while the switch S1 is connected to the cooking mode side shown in FIG. This is achieved by a control voltage generated from the output control circuit 14 in conjunction with the variable resistor 16.

In this case, the oscillator 2 is configured as a variable frequency oscillator, and the oscillation frequency, that is, the switching frequency of GCSL is switched by the first control voltage, and the rectifier circuit 9 is switched by the second control voltage supplied to the trigger circuit 13. The output power is controlled by switching the rectification operation between full-wave rectification and half-wave rectification. FIG. 4 is for explaining such output power control.

First, if the variable resistor 16 is continuously rotated from the lowest output position to the highest output position, the output control circuit 1
4 to a certain rotational position corresponding to 600W, the level changes continuously from the V1 level to the V2 level, and when the rotation is made further, the level changes from the V1 level to the V2 level again. A first control voltage is generated that varies depending on the voltage. This first control voltage is applied to the oscillator 2 as a control voltage, and the oscillation frequency is changed to F2 as shown in FIG. 4B.
It decreases from 1 to f1, increases to F2 again, and decreases to f1. When the first control voltage once rises to V2 and then falls to V1, a second control voltage rising from the low level VL to the high level VH is generated as shown in FIG. 4C. By supplying the second control voltage to the trigger circuit 13, the rectifier circuit 9 performs half-wave rectification operation when the second control voltage is V9, and performs full-wave rectification operation when the second control voltage is V9. controlled to do. As shown in FIG. 4D, the output power is (P1-P2-
P3) is continuously increased. As an example (P1=30
0W. ．． P2=600W, , P3=1200W). From the cooking mode in which the output power is controlled in this way, when the output adjustment knob is turned all the way to the left as shown in FIG. 3 and the slider of the variable resistor 16 in FIG. 1 is located at the end, The cooking and warming mode switching switch S1 is switched from the cooking mode shown in FIG. 1 to the warming mode.

In this heat retention mode, the control voltage obtained from the variable resistor 17 provided in the heat retention control circuit 15 or the control voltage output terminal 3
7 to the output control circuit 14. At the same time, a control voltage is supplied from the on/off control voltage output terminal 44 to the trigger circuit, thereby controlling the on/off of the output power, and as a result, the temperature of the pan 5 is maintained at a substantially constant set heat retention temperature. Ru. The function of the heat retention control circuit 15 in this heat retention mode will be explained with reference to FIG.

FIG. 5 shows the connection configuration of the heat retention control circuit 15. The variable resistor 17 for temperature adjustment has one end of its stator connected to the power supply terminal of the power supply voltage (+■CC:12■) and the resistor 32.
The other end is grounded through a series circuit of a resistor 33 and a thermistor 18. The slider of this variable resistor 17 is connected to the base of an emitter follower type transistor 35 via a diode 34, and also to the base of an emitter follower type transistor 36. A control voltage output terminal 37 is led out from the emitter of transistor 35. Further, the emitter of the transistor 36 is connected to the base of one transistor 40a of the Schmitt circuit 39 via a diode 38. The base of this transistor 40a is also connected via a diode 41 to a connection point between a resistor 42 and a thermistor 19. The base of the transistor 43 is connected to the collector of the transistor 40b of the Schmitt circuit 39, and the collector of the transistor 43 is connected to the output on/off control voltage output terminal 44.
It is derived as In the switch S1, in the heat retention mode, the movable contact a connected to the power supply terminal is connected to one fixed contact b, as shown in the figure, and in the cooking mode, the movable contact a is connected to the other fixed contact c. There is. A fixed contact b of this switch S1 is connected to a movable contact d of the tempura switch S2. In the tempura switch S2, the movable contact d is connected to the fixed contact e in the normal warming mode, and the movable contact d is connected to the fixed contact f in the tempura mode. Depending on the connection state of these switches S1 and S2, the transistor 45 as a switching element,
The on/off states of 46 and 47 are controlled and the variable resistor 1
The connection state of the circuit network including 7 and the value of its combined resistance are changed according to each mode. In addition, fixed contact c of switch S1'' and fixed contacts E and f of switch S2
is connected to a display control circuit (not shown) as shown by the arrow, and is configured to selectively light up the heat retention mode display lamp 30 and the tempura mode display lamp 31 provided on the aforementioned operation surface. First, in the normal heat retention mode, as shown in the figure, the movable contact a of the switch S1 is connected to the fixed contact b, and the movable contact d of the snow switch S2 is connected to the fixed contact e.

Therefore, at this time, transistors 45, 46, and 47 are all off, resulting in the equivalent circuit shown in FIG. A resistor 48 inserted between the connection point of the variable resistor 17 and the resistor 33 and its slider is for correcting resistance change characteristics. The voltage of the slider of this variable resistor 17 is applied to the output terminal 37 via a diode 34 and a transistor 35.
is taken out as a control voltage. This control voltage corresponds to the control voltage shown in FIG. 4A for controlling the output power described above. The voltage of this slider is also applied to the Schmitt circuit 3 via a transistor 36 and a diode 38.
9 is supplied to the base of transistor 40a. In this normal warming mode, the temperature of the pan 5 is initially at the 9th temperature.
As shown by the broken line in the figure, it is assumed that the temperature is considerably lower than the set heat retention temperature TO.

At this time, the resistance value of the thermistor 18 is large and the voltage across the slider is sufficiently large. Therefore, the base potential of the transistor 40a of the Schmitt circuit 39 is higher than the reference voltage determined by the resistance ratio of the resistors 49 and 50, so that the transistor 40a is on and the transistor 40b is off. Therefore, the transistor 43 is off, and the output on/off control voltage generated at the output terminal 44 is 0■, which is the trigger circuit 1.
3, the output is turned on. On the other hand, since the voltage supplied to the base of the transistor 35 via the diode 34 is also high, the control voltage generated at the output terminal 37 is also high. Therefore, the rectifier circuit 9 performs a full-wave rectification operation, and the output power becomes approximately maximum (1200 W) as shown by the solid line in FIG. As a result, the pan 5 is rapidly heated and its temperature increases. As the temperature of the pan 5 increases, the resistance value of the thermistor 18 decreases, the voltage across the slider of the variable resistor 17 decreases, and the control voltage generated at the output terminal 37 decreases.

The temperature of pan 5 further increases and the output power increases to 600~V.
When the voltage on the slider decreases to such an extent that the voltage on the slider decreases to the point where transistor 35 turns on. At this time, the output terminal 37 is grounded. In this state, the output control circuit 14 and the trigger circuit 13 act to cause the rectifier circuit 9 to perform a half-wave rectification operation, and the output power is kept constant at 300 W, which is the minimum output power.
When the temperature of the pan 5 rises and reaches the set heat retention temperature TO, the Schmitt circuit 39 is reversed and the transistor 40a is turned on.
is off, the transistor 40b is turned on, and therefore the transistor 43 is turned on, and the output on/off control voltage generated at the output terminal 44 becomes the power supply voltage +Vcc. By supplying this to the trigger circuit 13, the trigger circuit 1
From 3. Trigger pulse no longer occurs and SCRll
A and llb are both turned off, resulting in an output-off state.
Further, at this time, since a series circuit of a diode 51 and a resistor 52 is inserted in parallel with the resistor 49 in order to turn on the transistor 43, the reference voltage supplied to the base of the transistor 40b becomes slightly higher. The temperature of pan 5 is the set heat retention temperature T. When the base voltage of the transistor 40a becomes higher than the reference voltage, the Schmitt circuit 39 is inverted and the output on/off control voltage becomes O.
(2), the output is turned on, and an output power of 300W is generated. As a result, the pot 5 is heated to the set temperature T. The output is turned off at . Thereafter, such operations are repeated to maintain the temperature of the pan 5 at approximately TO. Next, the tempura mode in which the tempura button 28 is pressed in the heat retention mode to connect the tempura mode switch S2 to the contact f side will be described.

In this case, the power supply voltage is applied to the bases of the transistors 35 and 45, turning off the transistor 35 and turning on the transistors 45 and 46. Therefore, the equivalent circuit at this time is as shown in FIG.
A diode 53 and a resistor 54 connected to the base side of
A resistor 55 is connected to the collector of the transistor 45 in parallel to the variable resistor 17, and resistors 56 and 48 are connected to the collector and emitter of the transistor 46. Variable resistor 17
It is inserted between both ends of the slider and its stator. Resistors 48, 56, and 57 are provided to correct the resistance change characteristics of variable resistor 17, and the value of resistor 54 is sufficiently smaller than the series resistance of resistor 32 and variable resistor 17. In the tempura mode represented by such an equivalent circuit, the resistor 54 with a small value is connected in parallel to the series circuit of the resistor 32 and the variable resistor 17, so that the resistance of the variable resistor 17 is different from the normal warming mode. Even if the position of the slider remains the same, the magnitude of the voltage extracted from the slider increases by a predetermined amount.

Therefore, the transistor 40a of the Schmitt circuit 39 becomes difficult to turn off unless the pan 5 becomes higher in temperature and the resistance value of the thermistor 18 becomes smaller than in the normal heat retention mode. Therefore, by selecting a predetermined amount by which the voltage of the slider of the variable resistor 17 increases in the tempura mode compared to the normal warming mode, the set warming temperature in the tempura mode can be made 100'C higher than the normal temperature. be able to. Further, since the transistor 35 is turned off in the tempura mode, the control voltage obtained at the output terminal 37 is the maximum, and the output power is the maximum, 1200W. That is, in the tempura mode, the output power is kept constant at 1200 W as shown by the solid line in FIG. 10, and the temperature of the pot 5 rises to the set warming temperature T as shown by the broken line in the same figure. When this happens, the Schmitt circuit 39 is activated in the same way as in the normal warming mode.
The output on/off is controlled by the control voltage generated at the output terminal 44 based on the comparison operation by the set heat retention temperature T. is kept approximately constant. In addition, in the normal keep-warm mode, if the temperature of the pan 5 is considerably lower than the set keep-warm temperature as in the above example, the output power is increased and the set keep-warm temperature T is increased.
Since the output power is reduced in the vicinity of O, the pot 5 reaches the desired heat retention temperature in a short time, and thereafter, the temperature can be kept small.

In addition, in tempura mode, the output power is increased because the heat retention temperature is high. Further, in the cooking mode, the switch S1'' is connected to the contact c, so that a forward bias is applied to the base of the transistor 47 through the diode 57 and the resistor 58, and the transistor 47 is turned on.

Therefore, the equivalent circuit at this time is that the variable resistor 17 is short-circuited by the transistor 47 as shown in FIG. At this time, the voltage supplied from the slider to the base of the transistor 40a of the Schmitts circuit 39 is applied to the resistors 32, 33, 58 and the thermistor 1, regardless of the position of the slider.
8 and diode 57. The value of the resistor 58 is selected to be sufficiently small compared to the resistor 32, so that when the temperature of the pan 5 becomes high, for example, 250°C or higher and the resistance value of the thermistor 18 becomes sufficiently small, the Schmitt circuit A control voltage for turning off the output is generated from 39. This is to prevent the pan 5 from becoming abnormally hot due to dry cooking. Note that when the surface temperature of the heating coil 4 reaches a high temperature, for example, 180° C. or higher, the resistance value of the thermistor 19 becomes sufficiently small to generate a control voltage to turn off the output, thereby protecting the heating coil 4. There is.

An example of the values of each resistor in the embodiment of the present invention described above is shown below.

However, the unit is KΩ. Variable resistor 17:50 Resistor 32:27 Resistor 33:1 Resistor 48: Resistor 54:4.3 Resistor 55:20 Resistor 56:22 Resistor 58:1.8 Also, thermistor 18, 19 is about 200K at 20'C
Ω, approximately 100KΩ at 40'C, 2.82K at 1500C
This is a characteristic of Ω.

As is clear from the above, the present invention has a heat retention function and can switch this heat retention temperature in two ways by operating a switch.Especially when applied to a heating device for cooking, the present invention has a heat retention function. In addition to the heat retention mode, there is the benefit of realizing a function to keep the temperature of the oil constant in tempura.

[Brief explanation of the drawing]

Fig. 1 is an overall block diagram of an embodiment of the present invention, Fig. 2 is a sectional view of the heating section, Fig. 3 is a perspective view of the main part of the operation surface, and Fig. 4
The figure is a route diagram used to explain output power control, Figure 5 is a connection diagram of the main parts of an embodiment of the present invention, Figures 6 to 8 are equivalent circuit diagrams used to explain Figure 5, 9 and 10 are route maps used to explain the heat retention operation. 2 is an oscillation circuit, 4 is a heating coil, 9 is a rectifier circuit, 13 is a trigger circuit, 14 is an output control circuit, 15 is a heat retention control circuit, 16 is a variable resistor for output adjustment, 17 is a variable resistor for temperature adjustment , 18, 19 are thermistors, 39 is a Schmitt circuit, SL, SL'' are switches for switching cooking and warming modes, and S2 is a tempura mode switch.

Claims (1)

[Claims] 1 Consisting of a first resistor, a temperature-sensitive resistance element whose resistance value changes depending on the temperature of the heated object, which is provided near the heated object, and a variable resistor, and connected between the terminals of a pair of power sources. a first series circuit having a first switching element and a second resistor connected in parallel to the variable resistor; a second series circuit having a first switching element and a second resistor connected in parallel to the variable resistor; a switching element, a comparison circuit that compares the voltage obtained at the slider of the variable resistor with a reference voltage, and a control circuit that controls the supply of power to the heating section based on the output of the comparison circuit, When the first and second switching elements are off, the temperature of the heated body is maintained approximately at the temperature set by the voltage obtained from the slider, and when the first switching element is on, the The voltage obtained at the slider is increased or decreased by a predetermined value so that the temperature of the heated object is increased or decreased by a predetermined amount, and the second
When the switching element is on, the variable resistor is short-circuited to maintain the temperature of the heated object at approximately a predetermined value.